Question: Rewrite ${((7^{9})(9^{-4}))^{-10}}$ in the form ${7^n \times 9^m}$.
Solution: ${ ((7^{9})(9^{-4}))^{-10} = (7^{(9)(-10)})(9^{(-4)(-10)})} $ ${\hphantom{ ((7^{9})(9^{-4}))^{-10}} = 7^{-90} \times 9^{40}} $